1. Field of the Invention
This invention relates to methods and apparatus for producing extruded products incorporating longitudinal stripes in their sidewalls, said stripes being useful for color coding, i.e., identification, as well as for decorative purposes.
2. Description of the Prior Art
For purposes of illustration, detailed reference will be made herein to the provision of electrically insulating coatings for cable, as representing one important field of use of the type of extruded products with which the invention is concerned. The invention, however, is readily applicable to other products such as extruded pipe as well as other extruded shapes. It will be understood that the term "cable" embraces both single- and multi-strand metal electrical conductors, regardless of gauge or cross-sectional shape. It will also be understood that the term "polymer" embraces both thermoplastic and thermosetting materials including rubber and rubber-like materials.
Coloring the exterior surface of the insulating coating of cable is a common method used to identify specific cable used for specific purposes. For example, it is often a common practice to use cable with a black or gray (non-colored-coded) exterior insulating coating as a conductor and cable with a yellow (color-coded) exterior insulating coating as a ground. In most production facilities, color-coded as well as non-color coded cable are produced with the same equipment. Inherent in this set-up are lost production time and, consequently, increased costs to change over from producing one type of cable to the other due to the fact that such change over generally necessitates shutting down and cleaning out or purging the extruder. The invention disclosed herein provides an effective substitute product for the conventional color-coded cable, i.e., a multi-striped color-coded cable, while avoiding the delays and increased costs inherent in producing the conventional solid-colored, color-coded cable.
Methods and apparatus have been disclosed for producing striped cable the most pertinent of which is believed to be disclosed in the patent to Stocker, U.S. Pat. No. 2,779,970. Although this patent relates generally to the production of striped cable, it neither discloses, suggests, nor renders obvious the invention disclosed herein. Stocker disclosed apparatus for extruding strand-shaped structures of a plurality of helically arranged colors, including surrounding cable with an insulation helically subdivided into two or more colors, but did not disclose or suggest the dispensing ring or related apparatus of the present invention, nor the methods for employing the same. U.S. Pat. No. 3,720,747 to Anderson et al also discloses a method and apparatus for producing striped cable, but in no way suggests the present invention.
The patents to Myers, U.S. Pat. No. 3,860,686 and Dougherty, U.S. Pat. No. 3,903,233, disclose methods and apparatus for extruding plastic insulating materials upon continuously advancing filaments, including wire, that include techniques for balancing the flow of the insulating material to insure a uniform coating of the advancing filament. Neither of these patents, however, either separately or combined, disclose, suggest, or render obvious the dispensing ring and related apparatus and methods of the present invention.
It is well known in the art to produce various extruded shapes, particularly sheet products, with a multitude of colors. Examples of such products along with the apparatus for producing same are disclosed in prior U.S. Patents such as U.S. Pat. Nos. 2,808,617; 3,715,420; 3,914,362; 4,072,791; and 4,074,958. It is also known in the art to superimpose layers of coating on a cable and in doing so to apply coatings with different colors. Examples of apparatus or methods for doing this are disclosed in U.S. Patents such as U.S. Pat. Nos. 2,859,476; 3,024,494; 3,222,721; 3,737,490; 4,032,381, and 4,093,414. None of these patents, however, separately or combined, disclose, suggest or render obvious the present invention.